Selecting apparatus for remotecontrol systems



Oct. 22,1946. L. v. LEWIS SELECTING APPARATUS FOR REIOTE CONTROL SYS'IEIS Original Fil ed larch 6, 1943 .5 Sheets-Sheet 1 iNVENTOR [loyd V. [ewzsz BY aim MTQRNEY 3 L. v. LEWIS Oct. 22, 1946.

SELECTING APPARATUS FOR REMOTE CONTROL SYSTEMS Original Filed March 6, 1943 5 Sheets-Sheet 2 H11 ATTORNEY L. V. LEWIS Oct. 22, 1946.

SELECTING APPARATUS FOR REMOTE CONTROL SYSTEMS Original Filed March 6, 1943 5 Sheets-Sheet 3 INVENTOR [loyd Vlezpzls".

H11 ATTORNEY L. v. LEWIS Oct 22, 1946.

'SELECTING'APPARATUS FOR REMOTE CONTROL SYSTEMS 5 Sheets-Sheet 5 Original Filed March 6, 1943 w w $3 ME QE &\

INVENTOR 9 Patented Oct. 22, 1946 SELECTING APPARATUS FOR REMOTE- I CONTROL SYSTEMS Lloyd V. Lewis, Pittsburgh, Pa-., assignor to The Union Switch & SignalCompany, Swissvale, Pa., acorporation of Pennsylvania Original application March 6, 1943, Serial No.

478,252. Divided and this application August: 12, 1944, Serial No. 549,277

17 Claims.

My invention relates to selecting apparatus for remote control systems, and more particularly to centralized trafiic control system for railroads in which a central ofiice is connected with a plurality of field stations by line Wires over which code signals are transmitted at times for controlling selected devices at the stations, and at other times for indicating the condition of station devices at the ofiice.

This application is a division of m copending application, Serial No. 478,252, filed March 6, 1943, for Remote control systems, and is an improvement upon that disclosed in my Letters Patent of the United States No. 2,229,249, granted January 21, 1941, for Remote control systems.

Qne object of my invention is the provision of a remote control system which is particularly adapted to the use of existing line wires without interfering with their joint use for telephone or telegraph communication or for other purposes. To this end the system of my invention employs code signals of the alternating current type in which each code comprises a series of impulses of current of alternately opposite polarity and the time spacing of successive impulses determines the code character. One advantage of this type of .code is that the line signals may be generated inductively and onsequently no line battery is needed.

- Another advantage is that signals of this type will pass readily through transformers or repeating coils, permitting line circuits to be used which are not available for battery'systems. My system, however, does not require the insertion of any apparatus in series with the line, nor is a metallic connection to the line wires essential. Furthermore, the apparatus at the ofiice and at the several stations is connected to the line wires in parallel and theoperation of the system is independent of the relative location of the ofiice and the several stations, one advantage of which is that in the event of an interruption due to a break in the line service may be quickly restored by-main ofi'lce switching, for example, by connecting the line in parallel with a spare line at its opposite ends.

A feature of my invention comprises the provision of interference preventing means which serves when two or more codes are initiated at the same time to effect their transmission sequentially in a given order, and also to stop the transmission of a .code which is interfered with by impulses of foreign current. The interrupted code may then be reinitiated manually or automatically for retransmission in its entirety.

Another feature of my. invention relates to the more efficient utilization of the code elements. In the system of the prior patent mentioned, only the long steps of the code are registered and for a system capacity of 35 stations seven steps of the codeare used- In the system herein disclosed, both the short and long code elements are registered positively and the number of available combinations is greatly increased, six Steps for example, being sufficient for the selection 01"64 stations. In respect to this feature, my invention is an improvement upon that shown in Letters Patent of the United States to Snavely et al., No. 2,183,155, issued December 12, 1939,- for Bemote control systems. i

Another feature of my invention relatesto a reduction in the number or 'relays'required for selectingv purposes. The selection of the stations isefiectedby the operation of 9, group of pilot relays, and generally requires but one such relay foreaoh selectingstep of the code. The opera tion of the pilot relays is so checked as to permit their utilization in both the picked u and released positions. I

Another feature of my invention comprises the provision of a pair of relays of the stick polar type arranged to remain in their last operated position when deenergized, for registering the shorter long character of the code elements. Theserelaysare operated alternately by the code elements as received and serve to store their characterfor delivery to the proper storage relay whilethenext element in turn is being received. Another object of my invention resides in provisions for allowing only one code to be stored at thecontroloiiice at a time, thereby insuring that a series of codes set up manually in a given order will be transmitted in the same order rather than in an arbitrary order of code superiority. This arrangement is of advantage, for example, in the operation of a series of track switches to set up a route and in efiecting the clearing of a signal governingtra'ffic movements over the route assoon as it is fully. set up and eliminates the need-"fora rout e circuit network for governing the order of transmission of the codes as-rediiired'heretoiore: In accordance with this feature of my invention the characterof the code to be transmitted is determined by the momentary operation of a selected starting button without theuse of individual codedetermining or starting relays as generally used heretofore. The apparatus is also arranged'that thelatter may be used to store a plurality of codesfo'r transmis- 3 sion in a fixed order without interference when desired.

The system of my invention employs a chain of counting relays similar in number and arrangement to those of my prior patent, but includes novel arrangements for governing the operation of these relays to render them responsive only to a particular code, no other selecting relays being needed except when it is desired to have them respond to more than one code.

Another feature of my invention resides in the connection of the stick polar relays for registering code character, in series with the counting relays, whereby each counting relay together with the polar relay energized in series therewith functions like a polar-neutral relay in providing checks against improper operation. That is to say, those circuits which include polar contacts also include neutral front contacts the closing of which checks the energization of the polar relay in the normal or reverse direction and thereby indicates that its contacts are in a proper position.

Another feature of my invention resides in improved arrangements for controlling a transmitter relay for generating the code, in which each operation of the relay depends upon the closing of a different one of a series of successively prepared circuits.

Another feature of my invention relates to the provision of improved means for preventing unclue delay in the transmission of codes from the different stations under conditions of heavy traffic, due to the fact that the stations normally have access to'the line in a fixed order of code superiority.

A leading object of my invention is the provision of a system of the desired scope in a form which can be readily maintained to minimize service interruptions and which is readily adaptable to widely different conditions. On the one hand, maintenance is facilitated by mounting the relays in one or more unit housings with detachable connections, while on the other hand, different conditions require a variety of units some of which may contain idle'relays and may be more efficiently provided for by the use of separately'mounted relays wired individually according to their location. To meet these diverse requirements those relays which are invariable, that is to say, those the functioning of which is required regardless of their location or of the scope of the installation are mounted in a detachable coding unit such as is provided in the system of my prior patent, having detachable connections to which those storage relays may be connected which vary according to the locainstallations in which they are not required for station selection.

I shall describe one form of apparatus embodying my invention and. various modifications thereof, and shall then point out its novel features in claims.

In the accompanying drawings,

Figs. 1A and 1B taken together, show in con- 4 densed form the apparatus at the control ofllce in a typical centralized traflic control system embodying my invention, Fig. 1A showing the ofiice coding unit and Fig. 1B the associated office storage apparatus.

Figs. 2A and 2B, taken together, show the corresponding apparatus at a typical field location, Fig, 2A showing a coding unit which is structurally similar to that at the office but which has different terminal connections, and Fig. 2B the storage apparatus at a station having only one unit group of devices to be controlled, each such group being identified as a station.

Fig. 20 illustrates a modification which is to be substituted for Fig. 2B at each field location where the number of devices to be controlled exceeds the capacity of a single station or panel.

Fig. 3 shows a modification of the ofiice selecting circuits which may be substituted for a portion of IE, to provide for the storage of control codes for transmission in a given order, as hereinbefore referred to.

Fig. 4 shows a pair of relays which may be substituted for any one of the pilot relays P of the other views to obtain the requisite contact capacity when this exceeds the capacity of a single relay.

Similar reference characters refer to similar parts in each of the several views.

Referring to Fig. 1A, the reference characters Y and Z designate a pair of line wires which provide a line circuit for the centralized trafiic control system of my invention. It is to be understood that these wire extend continuously the length of the territory controlled by the centralized trafilc control system, and that they may be used jointly for telephone and telegraph communication like the similarly designated line wires shown in Letters Patent of the United States to Baughman et al., No. 2,303,875, issued December 1, 1942, for Remote control systems. The system of my invention utilizes the line wires to provide a channel for the transmission of low frequency alternating current of the order of six cycles per second, and communication between the ofiice and stations is effected by means of codes each comprising a series of alternations or impulses of alternateley opposite polarity having a low frequency of the order mentioned, with pauses interposed to provide code character. The C. T. C. line channel in its normal idle condition comprises the line wires Y and Z in series, with a connection bridged across the line wires through the coils l2 of a low pass filter and the high resistance windin of a line relay R at the office, as shown in Fig, 1A, and also at each station, as shown in Fig. 2A, the transmitting apparatus at the ofiice and at each station being normally disconnected from the line. Each line relay R is of the stick polar type, like relay OR of the above-mentioned Baughman et a1. patent, and is arranged to hold its contacts magnetically in their last-operated position when the line is idle and also during the pauses between successive impulses of a code, the contacts of each line relay R normally occupying their left-hand position, as shown.

Each coding unit, such as the one shown in Fig. 1A, includes transmitting apparatus governed by its line relay R, consisting of a starting relay ST, a master relay M, a transmitter relay T and an impulse transformer I3, this apparatus functioning as follows: Relay M is picked up, and is held energized to condition the coding unit for transmission, by momentarily energizin relay then completes a circuit from the supply terminal B- of a suitable local source of current over back contact. at of relay T andthrough the. lower primary coil of transformer IE! to the common return terminal C of the local source. At the same time the closing of front contact 0'! of relay M connects the secondary winding of transformer i 3 across the line wire Y and Z through the coils l2 andl2a of a low-pass filter and the closing of front contact 0 of relay M completes the first of a series of circuits governed by the associated line relay R in a manner hereinafter described, by means of which relay T is operated periodically at intervals spaced in accordance with the desired code. Each time relay T picks up, the operation of its contact at reverses the direction of the currentthrough transformer l3. The periodic operation of relay T thus causes transformer I3- to deliver induced impulses of alternately opposite polarity-to the line circuit, the time spacing of which characterizes the code. Each code normally comprises sixteen impulses, providing fifteen code elements of selectable character.

Each line relay R controls a group of slow release timing relays Ll, L2, LP, and LB, corre sponding to the similarly designated relays of my prior patent. The timing of these relays is governed by means of electronic rectifiers as shown, in the manner explained in the patent, the rectifiers also serving to prevent contact sparking and to minimize contact wear.

In response to the first impulse of a code, each line relay R reverses, and its right hand contact a completes a circuit from terminal B over back contact a of relay L2, back contact c of relay LB, through relay LI to terminal C. Relay L! then picks up and its contact a completes a circuit for relay L2, whereupon relay L2 picks up and cornpletes circuits over front contacts 0 of relays L2 and L! to pick up relays LP and LB, which relays, as will be apparent from the drawings, are arranged to pick up simultaneously and to release successively following the release of relay L1 or L2. When relay L2 picks up, its contacts a and d shift the circuit for relay L! to the left-hand contact a of relay R so that relay Ll becomes deenergized, and during the remainder of the code relay Ll is energized by relay R overfront contact c of relay LB when relay R is in its normal position, While relay L2.is energized over its own front contact a when relay R is reversed. Relays Li and L2 remain picked up during thebrief intervals between successive impulses constituting the short elements of the code, and one or the other of these-relays releases during each pause constituting a long element and they thus serve to indicate code character. Relay .LP is deenergized upon the release of relay LI or L2 and governs the length of the long code elements transmitted by the associated transmitter relay T. Relay LB is a bridging relay Whichremains picked up for the duration of a code and controls various local circuits as hereinafter pointed out.

Since relay R is normally deenergized, it may happen that it willbe reversed accidentally when the system is in its normal at rest condition as, for example, by an impulse of foreign current. If this occurs, relays Ll L2, LP, and LB will pick up as described and then relays Ll, LP, and LB will release in that order, relay L2 remaining picked up to close a local restoring circuit for relay R extending from terminal B at front. contact c of relay L2 over back contacts c and 1750f relays-Ll and LB andthe local winding of relay R to terminal C. Relay R will thereby bev restored to normal, reenergizing relays-Ll, LP, and- LB, and then the-timing relays will release in the order L2, LP, LB, and LI. Each code consists of sixteenimpulses and hence relay R is-operated to normal by the final impulse and the timing relaysrelease in the orderlast mentioned at the end of each code. A codemay be initiated onlywhen relays LI and L2 are both released, and it follows that successive codes are spaced by an interval which is materially longer than any in terval between successive impulses of a code.

Each line relay R also controls a chain of counting relays l to 8- and it for counting the code impulses, and in series therewith controls a pair of stick polar relaysKSl and KS2 which are operated to normal or reverse to register code character in accordance with the time spacingof the impulses. When relay R reverses in response to the first impulse of a code, the energization of relay Ll as above describedcompletes a cir- 'cuit from terminal Eat the right-hand contactb of relay R over front contact b of relay Ll through the upper winding of relayKSl, backcontact-a of relay LB, front contact g of relay Ll through relay I to terminal C. Relay l therefore picks up and relay KSI is held normal, as shown. Relay LBthen picks up and shifts the circuit for relays KSI and i to the branch path extending from the right-hand terminal of relay KSI over front contact a of relay LB, back contact I) of relay 2 and thence over the front contact a and winding of relay l to terminal 0.

If the first element of the code is short, relay KS l is left deenergized with its contacts normal as shown, when relay R is operated to the left by the secondimpulse, but if the first element is long, relay LI releases before the second impulse is received and the'closing of its back contact I) shifts the circuit for relay I to include the lower winding of relayKSl in place of its upper winding, thereby reversing the direction of energization of relay KS1 to cause the contacts of relay KS! to move to the right. In this case relay KS I is left deenergized with its contacts reversed when relay R is operated by the second impulse.

In response to the second impulse of a code relay R closes a circuit from terminal B at its left-hand contact b over front contacts 6 of relay LB and b of relay L2 through relay KS2, back contact a of relay 8, front contact 2) of relay I through relay 2 to terminal C, whereby relay 2 is picked up and relay KS2 energized in the normal direction as shown. If relay L2 releases before the third impulse is received, relay KS2 will be reversed thereby,.that is, relay KS2 is left deenergized in its normal or reverse position depending on whether the second element is short or long, while the third element is being received. Relays 3 to 8 are provided with circuits generally similar to those for relays l and 2 and are arranged to pick up one at a time in the same way in response to the corresponding impulses of the code, each inseries with relay KS1 or KS2 as described.

When relay 8 picks up, a chain repeat relay CR is energized over a circuit extending from terminal B at the front contact 1 of relayLB over contact 0 of relay 8 and the winding of relay CR to terminal C, and relay CR picks up completing a stick circuit'at its contact a whereby relay CR is held energized until the end of the and relays l to I operate through a second cycle in response to impulses 9 to of the code. Contact e of relay CR. serves to cause relay |6 to be operated in place of relay 8 in response to the sixteenth or final impulse. It will be understood that on each step except the last, relay KS! or KS2 is positioned to normal or reverse in accordance with the short or long character of the corresponding code element and is held deenergized in its last operated position to store the code character for the duration of the next succeeding code element. As explained in more detail hereinafter, contacts b of relays KS are included in circuit portions leading over wires 56-59 to coding unit terminals which may be adjustably connected externally to those terminals which lead over wires 22-21 to the right-hand terminals of the counting relay windings. These circuit portions provide selectively controlled connections to the common terminal C of the local source which serve during the first cycle of operation of the counting relays to prevent their continued response to a code to which the apparatus is not adjusted to respond and to check the positions of the pilot relays P of Fig. 13. During the second cycle of operation of the counting relays, the closing of contacts a and d of relay CR connects wire 56 to wire 58, and wire 51 to wire 59, and thus renders the operation of the counting relays independent of the position of contacts b of KSI and KS2, and during this cycle the pole changer contacts a and c of the relays KS control the polarity of the current supplied to a series of circuits prepared by the closing of front contacts ,1 and g of relay CR, completed externally by suitable connections to the coding unit terminals over wires 46-55, which as shown in Fig. 113 control the indication relays K. Relay KS1 also controls relay E in accordance with the character of the first element of the code, which is made a short element in each control code transmitted from the ofiice and a long element in each indication code transmitted from a field station. The energization of relay E conditions the coding unit to function as a receiver.

The application of the apparatus of my invention to a specific installation will now be explained, assuming for sake of illustration that it is employed in a centralized traific control system for controlling spaced groups of traffic governing devices such as the one shown in the track plan in Fig. 2B. This group comprises a track switch i'W and a group of signals LH and RH which as indicated diagrammatically on the drawings are arranged to be controlled by code by the operation of a group of polar stick relays including a switch control relay WS and the signal control relays LHS and RHS. It is to be assumed that the installation includes not more than sixteen such locations, each having a coding unit arranged as in Fig. 2A and connected by line wires Y and Z with one at the control office arranged as in Fig. 1A. At the location of switch IW, the coding unit connections are arranged precisely as in Fig. 23, this location being identified as station No. l, the connections at the other stations being differently arranged so that each is responsive to a distinctive code call.

At the office, the coding unit connections are arranged as shown in Fig. 1B, and include a control panel for each station containing the usual complement of control levers and indication V lamps, of which only the one for station No-1 is shown, this including a starting button IPB for initiating the transmission of a control code containing the code call for station No. 1, a switch lever SW and a signal lever SIG for controlling the switch and signal relays at station N0. 1, the levers being operatively associated with the coding unit by the energization of a selector relay OIS. The indication lamps of the panel are controlled by a group of indication relays K, which are operatively associated with the coding unit by the energization of a delivery relay OlD, energized in response to an indication code received from station No. 1.

Each code call comprises a distinctive combination of long and/or short steps, four steps providing sixteen such code calls. The ofiice coding unit is arranged to transmit control codes of sixteen steps or code elements, in which the first and second are short; steps three to six, comprising the code call, either short or long; and steps seven to fifteen either short or long, to selectively control nine devices at the selected station, step sixteen governing the return of the apparatus to normal at the end of the code. In the specific arrangement chosen for illustration the code call for station No. 1 comprises four long steps; the seventh step is used to control a maintainers call signal lamp MC, at the selected station, by closing a key MCB, and steps eight, nine, and eleven are used to control the relays WS, LHS,

and RHS in accordance with the positions of the control levers SW and SIG. The remaining steps, not needed for control purposes, are made short steps.

Each code call is set up for transmission by positioning a group of four pilot relays, P3 to P6, Fig. 1B, in a distinctive pattern, the contact d of each of these relays controlling relay T to generate a long step of corresponding number if the relay P is picked up and to generate a short step if such relay remains released.

The step by step transmission of a control code to station No. l, in response to the operation of the starting button IPB will now be described, assuming the control levers to occupy their normal positions as shown.

The transmission of a code by any coding unit may be initiated only when the coding unit is in its normal at rest condition, so that relays LI and L2 are both deenergized. In that case terminal B at back contact c of relay L2 is connected over back contact (1 of relay Ll to wire 11, and a code may then be initiated by connecting wires I1 and I5 together to complete a circult to pick up the starting relay ST,

Assuming that button IPB is operated, under the condition described, the connection from terminal B at wire I? will be extended over contacts b to e of button IPB to wires '13 to 16 and thence through the upper windings of each of the relays P3 to P6 to terminal C. Relays P3 to P6 pick up, as required for the code call of four long steps identifying station No. 1, and extend the connection from terminal B at wire I! over their contacts 0 to wire 15 and thence ,through relay ST to terminal C. Relay ST picks up, and completes a circuit from terminal B over its front contact 0, shown at the right in Fig. 1A, over back contact 1 of relay M to wire'2l and thence over contacts e of relays P3 to P6 in series, through relay OIS to terminal C, Relay OIS picks up, and the closing of its front contact 1' connects terminal B at contact I of button IPB to wire 28 to complete a circuit over front contact a of relay ST, back contacts 9 and hof relays LB and E through relay M to terminal C,

The energization of relay M over the circuit just traced, energizes the impulse transformer l3 and connects it. to the line as already explained. It is to be understood that when transformer i3 is energized over the branch including back contact 01 of relay T the resultant line impulse is of nor..- mal polarity to operate each line relay R to. the left, and when it is energized over front contact (1 of relay T the resultant impulse is of reverse polarity to operate each line relay R to the right. The initial impulse due to the closing of contact a of relay M therefore tends to operate the relays R. to the position they already occupy and is not part of the code, its purpose being toinsure the proper initial magnetization of transformer I3.

When relay OHS picks up, the opening of its back contact is extinguishes any of the indication lamps of the panel, such as lamp NH, which may be lighted, thereby indicating to the operator that the code has been initiated. When relay M picks up, it completes a stick circuit for the pilot relays P extending .from terminal B at front contact e of relay M to wire l9, and through the lower winding and front contact a of each of the relays P3 to P6, to wire l8, and thence to terminal C at back contact of relay E. The closing of front contact of relay M connects terminal B directly to wire 2|, to hold relay OIS picked up, and the operated starting button IPB may now be released.

As soon as relay M picks up, relay T becomes energized over the circuit extending from terminal B at contact 0 of relay M, contact 19 of re lay ST, through the winding of relay T and resistor 29 to terminal C, and relay T pick up to deliver the first impulse of the code to theline to reverse all line relays R. in unison, each of which operates its timing relays and counting relay I as already described. In the coding unit which is transmitting the code the energization of relay LB transfers relay M to a holding circuit having one branch extending frornterminal B over the normalcontact b of relay R and back contact I) of relay T, and another branch eX- tending from terminal B over the reversecontact b of relay R and the front contact b of relay T; thence over front contacts I) and g of relays M and LB, back contact h of relay E and the winding of relay M to terminal C. Relay ST becomes deenergized but is made sufficiently slow release by the provision of a rectifier unit asshown so that although its energizing circuit is opened when relay LI picks up, it remains picked up long enough to permit relay LE to pick up to complete the stick circuit for relay M. When relay T picks up it is held energized independently of relay ST over a stick circuit including its own front contact When relay I picks up, a connection extends from terminal B at contact 0 of relay M over back contact b of relay CR and front contact d of relay l to wire iii. The wires 3! to 55, inclusive, provide external connections for completing a series of circuits, closed one at a time by the counting relays, for controlling the periodic operation of relay T to determine the desired character for each of the elements one to fifteen, respectively, of the code. Any of these wires connected to te'rinihal B overa contact d or e of anodd-ninhbere'd counting relay may be connected externally to wire El or H to extend the connection of terminal 13 to the left-hand terminal of relay T so as to shunt the relay to cause it torel'ease. If the connection is made to wire El a short odd-numbered code element will be generated for the reason that relay T will be shunted as soon, as the corresponding counting relay picks up. .If the connection is made to wire H, a long element will be generated, relay T being held energized after the counting relay has picked up until relays LI and LP release and the connectionis completed by the closing of back contact 19 of relay The even-numbered code elements are similarly controlled by external connection to wires 60 and Hi. The second element, for example, will be ashort element when wire 32 isconnected to wire 69 because a circuit will be closed to pick up relay T, at back contact (2 of relay 1 as soon as relay 5 is released following the energization of relay 2. If on the other hand wire 32 is connected to wire iii, a long element will be generated, relay T remaining deenergized until relays L2 and LP release to close the pick-up circuit at back contact c of relay LP.

It follows therefore that after relay T is initially picked up by the operation of relay ST it continues to operate periodically to generate a code, provided relay M remains picked up and the associated counting relays respond. Each time relay T picks up itis, held energized over its stick circuit until the associated line relay R reverses to pick up an odd-numbered counting relay, contact d or e of which connects terminal B over wire 6! or H to the left-hand terminalof relay T to release it by short circuiting its wind ing. Each time relay T releases, relay R is operated to normal to pick up an even-numbered counting relay, whereupon the last operated oddnumbered relay releases to prepare a pick-up circuit for relay T closed over wire 60 or TU.

In the control code being described, the first step is short, due to the, fact thatrelay T is shunted by the connection over front contact d of relay l and wires SI and 6!, Fig, 13, as soon as relay I picks up, the code being thereby distinguished from an indication code transmitted from a field station which has a long first step. The second step is made a fixed short step by a connection over back contact d of relay 1 and front contact d of relay 2, over wires 32 and 60, over which relay Tis picked up in response to the release of relay l. The front contacts d of relays P3 to P6 are now closed, so that wires 33 to 36 are connected to wire "H3 or II and the closing of the circuits including the front contacts 11 of relays 3 to ii is delayed until relay LP releases on each of the steps three to six, thereby making these steps long. Assuming key MCB to be open, relay P! will occupy its released position, and the seventh step will be made short due to the connection from wire 5'! over back contact (1 of relay P1, to wire fil.

The code transmission continues through the seven steps as described only if the code delivered to the line by which relays KS! and KS2 are operated, is of the corresponding pattern. Unless the first step is short, the office relayE picks up as hereinafter described, and its back contact h opens the circuit for relay M to stop further transmission. Unless relay KS2 remains normal to register a short second step, relay 3 is not-operated, its circuit extending from its right-hand terminalover wires 22 and 56 to terminal C at the normal contact I) of relay KS2. Similarly, the operation of relay 4 is dependent upon the reversal of relay KS! to registerthe long third step, the circuit for relay 4 extending from wire 23 over front contact 17 of relay P3 to wire 59 and thence to terminal 0 over the reverse contact b of relay KSI. Relays 5 to l are con- 11 trolled over similar circuits including front contacts b of relays P4 to P6, while relay 8 is controlled over a circuit including back contact I) of relay PT. It follows therefore that the ofiice relay 8, and relay CR controlled thereby, is operated only if steps one to seven of the control code are of the desired character.

When relay CR picks up on the eighth step, its

contact b transfers the control of relay T from.

g the d contacts of the counting relays to a series of eight similar circuits extending from contacts e of relays 8 and I to 1, respectively, to Wires 38 to 45 extending over contacts b to i of relay OIS,

. for controlling the character of steps eight to fifteen in accordance with the positions of the levers of the selected panel in the same manner as the preceding steps are controlled by contacts cl of the relays P, as above described. The circuit for step eight, for example, extends from wire 38 over contact b of relay OSI and lever SW to wire 60 or '10, and is therefore made a short step if lever SW is normal and a long step if lever SW is reversed. The signal lever SIG controls the character of steps nine and eleven, both of which are made short when lever SIG is normal as shown. Step nine is made lon and step eleven short when lever SIG occupies its lefthand position, and step nine is made short and step eleven long when lever SIG occupies its right-hand position, as will be clear from the drawings. The remaining steps, in the specific arrangement described, are made short steps by the provision of direct connections from contacts d and f to z of relay OIS to wires 50 and BI.

The transmission of the code being described is terminated with the dropping of relay T to begin the sixteenth step, during which the apparatus returns to its normal at rest condition. Relay IE is the first to release, then relays L2, LP, and LB release. Relay LB releases relays M, CR, and LI, and relay M releases relays P3 to P8 and OIS, and finally, relay Li releases.

Considering now the manner in which the control code just described is selectively received at station No. 1, and referring to Fig. 2A, since a coding unit like that shown in this View is provided at each field location, each of which is similar to that of Fig. 1A except for its external connections, it follows that the line relays R and the timing relays at all stations operate in unison with the corresponding office relays in response to the control code, likewise relays I, 2, and 3.

Each station coding unit is conditioned to function as a receiver by the energization of its relay E on the second step, as hereinafter described.

At station No. 1, relays 4 to I pick up on the corresponding steps because wires 23 to 26 of Fig, 2B are connected to wire 58 or 59 and the circuits for relays i to I are similar to those established for the correspondin office relays when relays P3 to P6 are picked up, as already described.

It is to be understood that at each other station one or more of the wires 23 to 26 is connected to wire 56 or 51 instead of to wire 58 or 59, as illustrated in Fig. 2C, for example, and consequently at each such station the operation of the counting relays terminates before reaching the eighth step of the code containing the code call for station No. 1.

At station No. 1, however, the counting relays operate until the sixteenth step is reached, in unison with the oifice relays, and when relay CR picks up on the eighth step, a branch of its circuit is closed from terminal B over front contact b of relay E to wire 9, thence through relay MCR to terminal C, over the pole changer contacts e and f of relay Pl, whereby relay MCB is energized in the normal direction if relay P! is released, and in the reverse direction if relay P1 is picked up.

It is to be understood that relay MCB is of a magnetic stick type and that it closes its contact to light lamp MC when energized in the reverse direction, and assumes the released position when energized in the normal direction, remaining in its last operated position when deenergized.

Assuming the eighth step of the code being received to be short, relay KS2 will occupy its normal position and the polar stick relay WS of Fig. 2A will be energized momentarily in the normal direction at the beginning of the ninth step over a circuit extending from terminal B at the right-hand contact b of relay R, contact d of relay LB, normal contact a of relay KS2, contacts g of relays CR and E, contact 1 of relay I, wire 48, relay WS, wire 46 and thence to terminal C at the normal contact c of relay KS2. If lever SW had been reversed to make the eighth step long, relay KS2 would be reversed, and relay WS would be energized in the reverse direction on the ninth step. Relays LHS and RHS are similarly controlled in accordance with the character of steps nine and eleven, respectively, as reflected by the position of relay KSI, these relays being operated to normal or reverse on steps ten and twelve, as will be clear from the drawings.

Each station coding unit is adapted to be conditioned to transmit indication codes in response to the energization of a code storin stick relay, such as the relay l CS of Fig. 2B.

When relay ICS is energized, it connects wire I! over its front contact I) to wire 15, to which the starting relay ST of Fig. 2A is connected, and this relay ST when energized completes a connection from terminal B over wire 28 and its front contact a to pick up relay M. The energization of relay ICS thus corresponds to the operation of the starting button I PB in the control code already described, that is to say, it is effective When the system is at rest, to pick up relays ST and M to initiate the transmission of an indication code by relay T at station No. 1.

Relay l CS may be picked up in response to changes in the condition of any of the indicating relays at station No. 1, as hereinafter described in detail; but it is also picked up upon the delivery of a control code to station No. 1 over the circuit extending from terminal B at wire 9 through its upper winding to terminal C.

The transmission of a control code to station No, 1 will thus be followed by a transmission of an indication code from station No. 1, in which the operation of the station transmitter relay T, of the line relays R and of the timing and counting relays controlled thereby are generally similar to those already described. The indication code comprises sixteen steps in which the first is made a long step by connecting wire 3| to wire H, as shown in Fig. 2B, instead of to wire 6i. Wires 32 to 31, in Fig. 23, provide connections similar to those provided for the ofiice relay T in the control code described. Consequently steps two and seven will be short and steps three to six long, the connections of wires 33 to 36 to wire 10 or 1| providing for the transmission of the code call of four long steps identifying station No. 1.

It is to be understood that at each other station one or more of the wires 33 to 3B is connected to wire 60 or Bl, as illustrated in Fig. 2C, for example, to effect the transmission of different code calls.

When the coding unit of Fig. 2A is in the transmitting condition, terminal B at contact 6 of relay M is connected to wire l9, preparing a circuit which may be completed at contact a of relay R1 through the upper winding of relay P1 to terminal C, whereby relay P! may be controlled to make the seventh step short or long, in accordance with the position of an indicating relay R1. The circuit by which relay P1 is held energized in the receiving condition is ineffective when relay P1 is subject to control by relay R1, wire I8 being connected to terminal C, at back contact of relay E.

Steps eight to fifteen of each indication code may be used to indicate the condition of eight other station devices by suitable connections to wires 38 to 45. As shown, wires 38 to 42, controlling the transmission of steps eight to twelve, are connected to contacts (1 of the indicating relays NWP, LHR, RWP, BER, and TS, while wires 43, 44, and 45 are connected to wires 6|, 60, and El, respectively, so as to make these steps short. Since all the connections, except the one for the first step, are similar to those for the office relay T already described, no further description of the detailed operations involved in transmitting an indication code is deemed necessary.

Since the first step is long, relay E at the transmitting station is not operated. This is also true of relay E at each other field station, and consequently none of these are conditioned to receive the code.

Since each transmitter has access to the line when it is free, it may happen that two or more are set into operation at the same time. If this occurs, interference is avoided by stopping the delivery of impulses to the line by any coding unit which is transmitting a code if its line relay R is operated by a received impulse during a pause in the operation of the associated transmitter T. If relay R is thus operated to a position out of step with the relay T itcontrols, the stick circuit for relay M is opened at contact b of relay R, releasing relay M to disconnect the transmitter from the line, the coding unit then being in condition'to transmit its code in its entirety when the line is again free.

Since the line relays R are of the stick polar type, relay R at a station which is transmitting a long code element is temporarily deenergized and in condition to respond to an impulse received from the line as required for the operation of this feature. 1

It will be readily apparent, therefore, that the use of the line is allotted to the different stations in accordance with the relative superiority of their code calls, a short element taking precedence over a long element in each instance. Control codes transmitted from the office are given precedence over indication codes transmitted from the'stations by the provision of a short first element in each control code and of a long first element in each indication code, as already explained. Thus when a control code and an indication code are initiated at the same time, the

nection for shunting relay T at each field station includes wires: 3| and I I, it will remain open and the station relay T will remain picked up until the associated relay M is released to disconnecttransformer l3 at that station from the line, leaving the office transmitter in control to continue the code.

It has already been mentioned that the coding unit at each field location is arranged to receive control codes as identified by a short first element by suitable connections for relay E. Thus in Fig. 2A, wire I! is connected to wire [4, and since relay KS3 remains in its normal position, the station relay E: is energized in multiple with relay 2 at the beginning of the second step over a circuit extending from terminal B at the lefthand contact 22 of relay R, front contact e of relay LB, normal contact a of relay KSI, wires M and it, contact 0 of relay 1 and the upper winding of relay E to terminal C. Relay E therefore picks up, and completes a stick circuit over its contact a and lower winding, extending to terminal B at contact) of relay LB.

By referring again to Fig. 1A, it will be seen that the office coding unit is conditioned to recupies its reverse position during the second step only if the first element of the code is long.

Referring now to Fig. IE, it is to be understood that the key MCB controls the character of the seventh step of a control code initiated by the operation of any one of the buttons IPB to IBPB, to operate a maintainers call signal at the selected station, and the operation of this feature will now be described. Assuming that key MCB is closed, and that button IPB is operated, a control code will be initiated as already described. When relay M picks up, a circuit is closed from terminal B at its front contact e, Fig. 1A, over wire l9 and the contact of MCB, Fig, 1B, wire 11 and the upper winding of relay P1 to terminal C. Relay Pl therefore picks up, and its contact d shifts the connection of wire 31 from wire Bl to wire H, causing relay T to generate a longseventh step during which relay Ll releases to reverse relay KSI, the control code being in other respects similar to the on already described in detail.

At station No. l, the release of relay LI on the seventh step completes a circuit from terminal B at contact 1 of relay LiB, Fig. 2A, over back contact a of rela CR, front contact 6 of relay E, hack contact e of relay Li, contact 0 of relay 1, wire 61 through the lower winding of relay P1 of Fig. 23, to terminal C, so that the station relay P1 picks up completing a stick circuit over its contact a and wire l8, extending to terminal B at front contact 0 of relay E.

At the office and at station No. 1, a circuit is prepared for relay 8 extending from wire 21 over front contact I) of relay P1, wire 59 and the reverse contact b of relay KSi to terminal C, so that relays 8 and CR pick up on the eighth step and at station No. 1, terminal B is connected to wire 9, energizing relay MCR in the reverse direction over front contacts 6 and f of relay P1 to light lamp MC, as required. The remaining operations are similar to those occurring on the corresponding steps of the control code already described.

In describing the step-by-step operation of the system, it has been assumed that the apparatus of Fig. 1B has been arranged for sixteen stations, using the elements three to six of the code in different combinations of long and short elements to providethe sixteen code calls. Step two of the code is made a fixed short element by connecting wire 32 to wire 60. A pilot relay P is provided for each of the steps three to seven, having a contact d for controlling the transmission; that is to say, each of these steps is made long or short according to the position of the associated relay P. Relays, P2 to P6 may be arranged in sixteen different ways to complete a circuit from wire 2| over their contacts e to i to select any one of sixteen S relays, as indicated by the references OIS to OIBS, in Fig. 13.

By the addition of a pilot relay P2 to the group of relays P3 to P6, to control the character of the second step, the number of stations which the system is adapted to control is doubled, five steps providing code calls fOr thirty-two stations. Relay Pl, as shown, provides an additional control or indication element in each code, but this relay may be used for station selection by arranging its circuits like those for relays P3 to P6, and it follows that the system may employ codes having either five selecting steps and nine function control steps, or six selecting steps and eight function control steps, the latter arrangement providing for the control of sixty-four stations.

For the control of sixteen stations, as shown, the circuits controlled by contacts e to z of the relays P consist of two sets of circuits for eight S relays each, selected over front and back contacts e of relay P3. Similarly, to control thirtytwo stations, two sets of circuits for sixteen S relays, each set like the one shown, but connected to wire 21 over front and back contacts, respectively, of a relay P2, ma be used. To obtain the requisite number of contacts one or more additional relays may be provided for any of the steps. Thus for the two sets of sixteen circuits mentioned, relay P4 may be replaced by a pair of relays P4A and P43, having their windings connected in parallel and their contacts a in series, as shown in Fig. 4, likewise relays P5 and Pt. Any of the thirty-two circuits thus provided may be branched over front and back contacts of relay P1 to provide circuits for two S relays, as is obvious.

The pilot relays have a dual function. When the coding unit is in the receiving condition, with relay E picked up, the relays P are picked up one at a time in response to corresponding long elements of the code as received, and current is supplied to wire 2! by relay CR to pick up the selected relay S on the eighth step of the code.

The relays P also serve to condition the coding unit to transmit a code. That is to say, they may be set up in any desired combination and the corresponding S relay energized when the system is at rest by the operation of a starting button or code determining relay to initiate the transmission of a code, in which case the P relays determine the pattern of the station code call, as already mentioned.

The step-by-step operation of the apparatus of Figs. 1A and 1B in receiving an indication code will now be described. It will be assumed that the code received is one transmitted from station No. 1 as above described, in which steps one and three to six are long steps, and steps two and seven to fifteen are short, and it will be understood that the oflice line relay R responds to the received impulses and controls the associated timing relays, and that relays l and 2 respond as in the codes already described. Since the first step is long, relay KSI is operated to reverse in series with relay and its right-hand contact a prepares a circuit including wires 4? and Il over which relay E, Fig. 1A, picks upon the second step, the closing of front contact e of relay E prepares pick-up circuits for the relays P which may be traced from terminal B at contact 1 of relay LB, back contact a of relay CR, front contact e of relay E, back contact e of relay Ll or L2, contacts 0 of relays 2 to 7 and the corresponding wires 626l, through the lower windings of relays P to terminal C. In the case of relays P2 to P6, the connection to terminal C includes wire I9 and back contact e of relay M.

Since the third step is long in the code being described, relay P3 will pick up over wire 63 and front contact 0 of relay 3 in response to the closing of back contact e of relay LI on that step, and relays P4, P5, and P6 will pick up over corresponding circuits on steps four, five, and six. Since the seventh step is short, relay Pl remains released.

A stick circuit is completed by each relay P which picks up in response to the closing of back contact e of relay LI or L2, which includes its own front contact a and extends over wire I8 to terminal B at front contact 0 of relay E.

A check to insure against the failure of the relays P to assume the positions required for the code call being received is provided by the connections for the counting relays 3 to 8 which extend to terminal C over wires 22-47 and contacts b of the relays P, wires 56-59 and contact I) of relay KSI or KS2. In response to each long element, relay KSI or KS2 is reversed and completes a connection to terminal C over wire 58 or 59 andfront contact b of that one of the relays P WhlCh is picked up by the same long element, to prepare a circuit for the counting relay next to be operated. If the element is short, relay KSI or KS2 remains in its normal position and the relay P is not operated, and the circuit prepared for the next counting relay includes wire 56 or 51 and a back contact b of the relay P. In case a pilot relay such as P2 is omitted, as in the case being described, the corresponding wire such as wire 22 is connected directly to wire 56 or 58, and as shown, relay 3 responds to the third impulse only if the second step is short.

It follows that relay 8 responds to the eighth impulse of a code to pick up relay CR only when the relays P have been set up in a combination representing the code call received by the relays I to I and KS. If the first code element is long as assumed, so that relay E is picked up, relay ii completes a circuit extending from terminal B at contact J of relay LB, contact 0 of relay 8, contact b of relay E, back contacts 0 and f of relays ST and M, to wire 2|, and thence as already described in connection with Fig. 1B over front contacts e of relays P3--P6 and the winding of the selector relay OIS to terminal C. Relay OIS is thus energized in multiple with relay CR and the closing of front contact a of relay CR completes a stick circuit for holding both of these relays picked upuntil the end of the code. When relay OIS picks up, a branch of its circuit extending from terminal B over contact b of relay I E to wire 9 is closed at contact a of relay OIS through the winding of relay OI D to terminal 0, whereby relay OID is energized. The closing of .4. A. mmbl contact a of relay OID then completes a circuit for operating the indication relay K1 in accordance with the character of the seventh element, this circuit having a connection to terminal B at wire 9 whereby relay K1 is energized in the normal or reverse direction according to the position of contacts e and f of relay P1. The indication relays may be of the ordinary stick polar type, but preferably are of the type shown in Letters Patent of the United States to Agnew, No. 2,301,992, granted November 17, 1942, for Electrical relays, which relays are operable to their picked up and released positions by current of normal and reverse polarity, respectively, and are adapted to remain in their last operated position when derenergized.

Contacts b to 2', inclusive, of relay OID prepare circuits for operating the relays K connected thereto in accordance with the character of steps eight to fifteen of the code. For example, the operation of relay R to the right in response to the ninth impulse connects terminal B to contact a of relay KS2, which relay is then held deenergized in its normal or reverse position to store the character of the eighth element. Relay I picks up, completing a circuit from terminal B to terminal C over contacts a. and c of relay KS2, including contacts g of relays CR and E, contact 1 of relay I, wires 48 and 46, contact b of relay OID and the winding of relay NWK, whereby relay NWK is energized normal or reverse to correspond with the position of relay KS2. The operation of relay R to the left in response to the tenth impulse opens the circuit for relay NWK and connects terminal B to contact a of relay KSl, and also restores relayKSZ to normal and energizes relay 2, while relay KS2 is held deenergized in its normal or reverse position to store the character of the ninth element. Relay 2 completes a circuit from terminal B to terminal C over contacts a and c of relay KSI, including contacts 1 of relays CR and E, contact J of relay 2, wires 49 and 41, contact 0 of relay OID and the winding of relay LHK, whereby relay LHK is energized normal or reverse to correspond with the position of relay KSl.

The operations occurring during the remaining steps of the code are similar to those described, as will be readily apparent.

It follows that on steps eight to thirteen, respectively, relays Kl, NWK, LHK, RWK, RHK, and TK will each be operated to a position reflecting that of the corresponding indicating relay at station No. 1. Steps thirteen to fifteen are fixed short steps in the code being described, but 7 Y additional indication relays Kl3 to Kl5 may be provided for indicating the character of these steps if required. The operation of relay R to the left in response to the sixteenth impulse picks up relay l6, and contact 12 of relay l6 completes the circuit for operating relay Ki5 to a position in accordance with the character of the fifteenth element. Relay I6 is not provided with a stick circuit and releases after a short interval. Relay R remains in its normal position, consequently relays L2, LP, and LB release in that order. Re-

lay LB releases relays CR, E, OIS, and OID, and

th apparatus of Fig. 13, with reference more particularly to the upper right-hand portion of that view, which shows circuits controlled by the buttons for controlling the relays P'Z-PG as required by various code calls. Ihe front contacts I) to 6, etc., of buttons PB, which provide a connection from wire ll to wires 13-16, correspond to the long elements in each of the fifteen code calls set up by th operation of buttons IPB to ISPB. The sixteenth code call, assigned to button lliPB, does not require the energization of any of the relays P3 to P6. It followsthat the code combination assigned to each of the panels may be readily identified from the drawings.

Terminal B is connected to wire I1 only when the system is at rest, or at the end of a relatively long time interval following the sixteenth impulse of a code, as already explained, under which condition the operation of any of the buttons except lBPB extends the connection from terminal B to one or more of the wires i346 and thence through the upper windings of the corresponding relays P to terminal C, thereby energizing a relay P for each long element of the selected code call. The energized relays P by closing their contacts 0 complete a connection from wire 11 to wire E5 to pick up relay ST. The operation of button IGPB completes a connection from wire El over its contact b to Wire E5 to pick up relay ST without operating any of the relays P, the code call for this button comprising four short steps.

When relay ST picks up, a circuit is closed from terminal B at its front contact 0 over back contact 1 oi relay M to wire 2! to pick up the relay S which corresponds to the combination set up by the relays P, opening back contact k of the operated relay S to extinguish the indication lights of the selected panel. If the relays P have been positioned properly this panel will be the one containing the operated button. That is to say, relay OlS will be energized only if each of the relays P3 to Pt pick up in response to the operation of button lPB, whereupon terminal B at contact f of button IPB will be connected over contact 7' of relay OiS to wire 28 and thence over contact a of relay ST, to pick up relay M, thereby setting relay T into operation to transmit the code as already described.

It is to be understood that the connection to wire 28 over contactf of each of the starting buttons lPB to WEB includes contact 7' of the corresponding S relay. It follows that relay M will not pick up if, due to a fault, the pilot relays P do not occupy the positions. required for the code call identifying the operated starting button.

When relay M picks up, its front contact 6 connects terminal B over wire I9 and the lower windings and contacts a of the energized relays P2 to Ft to wire l8 and thence to terminal C at back contact 0 of relay E, and it follows that the operated button may be released as soon as relay M picks up to initiate the-code.

The condition of relays P2 to P5 cannotbe disturbed by further operation of any of the starting buttons PB because when a code is being sent or received, terminal B is disconnected from wire l2. 7

As previously explained, when relay M is picked up, wires 13l3'l afford connections over contacts cl of the counting relays to wires 5.5, El, 16, and II for governing the operation of, relay T to generate the first seven elements of the code, the character of the varia-ble elements being determined by the positions of the contacts (I of the pilot relays P in the circuits. At the beginning of the eighth step, contact I) of relay CR picks up to shift the circuits for relay '1 to contacts e of the counting relays and wires 38-45, and thence over contacts b to i of that one of the selector relays OIS to OISS which is energized, and contacts of the control levers of the corresponding panel to wires 50, GI, 10, and H, or directly to wire 60 or 6| when a control step is idle, and determines the character of the ninth to fifteenth elements, in the manner already pointed out.

When relay T drops in response to the energization of wire 45 to transmit the final impulse of the code, it remains released. Relay R therefore remains in its normal position, and relays i6, L2, LP, LB, and LI release in that order. Relay LB releases relays M, CR, and the energized selector relay S, and then relay M releases the energized relays P. Relay LI, which is the last to release, connects terminal B to wire I! to render the buttons PB effective to control the initiation of the next code.

It is to be noted that each operation of relay T to generate either a short or long code element is dependent upon the closing of a circuit over one of the wires 3 l3l or 3845. A failure of any of the circuits to close would make the element indefinitely long, allowing the timing relays to release as at the end of the code to reset the transmitting apparatus in its normal condition. A similar release at the receiving station prevents the registration of the uncompleted element.

It may readily occur that an indication code will be initiated by a station at the same time that a control code for a different station is initiated. Normally the control code will take precedence by reason of its short first element,

but if due to a fault, the short first element is 1 not properly transmitted the station transmitter will retain control of the line to deliver a long first element. If this occurs, the office relay E will pick up in response to the second impulse as in the case of a normal indication code, releasing the office relay M by the opening of back contact 71. of relay E. Those relays P at the ofiice which were picked up to initiate the code will new release, due either to the dropping of relay M or to the reversal of polarity of the current supplied to their stick circuits over wires 18 and I9, when relay E picks up. It follows that the ofiice apparatus will be conditioned at the beginning of the second step to respond to the received code, that is, to pick up the relay P for any of the steps two to seven in accordance with the code as received.

It may also happen that two or more starting buttons are operated at the same time. The code determining contacts controlled by the starting buttons and connected to wires 12l6 are so arranged,.however, that irrespective of the number of sets operated, only one set of code determining contacts is effective to determine the code and no interference occurs, due to the pro-v vision of novel circuit arrangements as will now be explained.

By reference to the drawings it will be seen tion of any higher-numbered button. Similarly, when button SPB or 4PB is operated, the opening of back contact (1 of the operated button prevents the energization of wire 15 by operation of any higher numbered button. In place of back contacts in the sets of code determining contacts, back contacts of the P relays may be used with th same eifect; thus back contacts 1 and g of relay P3, which open in response to the operation of relay P3 by any of the buttons 5PB-8PB,

prevent the energization of wires 14 and 15 by operation of any higher numbered button. It will be clear from the drawing that the sets of code determining contacts are connected to the conductors 13-11 in such an order that they are efiective only one set at a time, in a fixed order of code superiority.

It is believed that the modification of the code determining circuits to provide code calls of five or six steps as required for the control of additional stations will be obvious from the circuits as shown. Thus, for example, to control thirtytwo stations, two groups of sixteen contact sets each may be used, each similar to the one shown except that in one group each set will have an additional contact for energizing relay P2, while the contacts of the other group will be connected over back contacts I to i of relay P2, as indicated by dotted lines in Fig. 1B.

In certain applications of the centralized traffic control system of my invention, particularly in connection with the control of train movements on single track railroads, it may be preferable to provide for the storage of codes at the control ofiice so that when several starting buttons are operated in a rapid sequence the codes will be transmitted in order without further attention, as in the system of my prior patent. This may be accomplished by the provision of a code determining relay CS for each panel, each controlled as shown in Fig. 3. 1 In this modification the contacts I to f of each starting button are replaced by similarly functioning contacts of the associated relay CS in the circuits of Fig. 1B, each starting button having only a single contact a. In this modification a storing relay such as OICS is picked up at once in response to the operation of the associated button IPB regardless of the condition of the coding apparatus, and is then held energized over the stick circuit extending to terminal B at back contact m of the associated selector relay OIS. When wire I! becomes energized, contacts I) to f of the lowest numbered one of the operated relays CS will be effective to operate the P relays as required to pick up the associated selector relay Sand to connect terminal B to wire 28 to initiate the code as described in comiection with the circuits of Fig. 1B, as will be readily apparent. In response to the operation of relays P3 to P6 by relay OICS for example, relay OIS is picked up and its contact m inserts back contact a of relay it in the stick circuit for relay OICS as shown in Fig. 3, whereby the circuit is opened to release relay OICS in response to the transmission of the sixteenth impulse of the corresponding control code to allow the next energized relay CS in order to initiate the next code to be transmitted. I

A contact 7' of the associated delivery relay OID provides a connection to terminal B which serves to prevent the release of relay OICS by relays OIS and I6 at the end of an indication code, in the event that the starting button IPB 21 is operated and relay OICS picked tip, during the reception of an indication code.

Referring now to Fig. 2B, it has already been explained that this view together with Fig. 2A shows an arrangement suitable for use at a field locationhaving a limited number of controlled devices within the capacity of a single ofiice control panel such as the one shown in Fig. 13, these devices being those required for the control of a single track switch IW, and a group of signals LH and RH, located at one end of a passing siding on a single track railroad, as indicated by the track plan shown. Suitable circuits for the safety control of such'devices are well known, one arrangement being shown, for example, in my prior patent hereinbefore referred to, and accordingly these circuits are shown herein only in diagrammatic form, to indicate how a typical group of traffic governing devices maybe controlled by code by means of stick polar relays. Wires 46-5-5 leading to the coding unit of Fig. 2A provide circuits for the control of eight stick polar control relays, of which but three are required for the simple layout shown, namely, the switch control relay WS which governs the operation of the switch machine ISM, and the signal control relays LHS and RHS which govcm the signal relays LHR and RHR to clear the signals for the desired direction of traffic movement and for putting'the signals manually to stop.

It has also been explained that the apparatus of Fig. 2B is arranged as required at station No. 1 by :connecting wires 22-21 to wires 5659 in such a manner as to render the counting relays selectively responsive to the code call set up -by operation of the starting button IPB of Fig. 113. It will be apparent that the operation of the counting relays will be discontinued on one step or another of any control or indication code containing a different code call. More particularly,

the station relayE responds to a short first element, indicating the office as the place of origin, and relay CR responds only if the second element is short and elements three to six are long, indicating station No. las the intended destination, and if relay P1 corresponds in position to the character of the seventh element as received. Since the station coding unit in this case responds selectively to only one code call, selector and delivery relays corresponding to relays OIS and 01D are not required, the closing of the contacts 7 and g of relays CR and E in the circuits including wires 4655 being sufiicient to indicate the selective response of the coding unit. Inother respects the circuits for controlling the stick polar relays such as WS are similar to those for the indication relays K of Fig. 1B, as will be readily apparent.

Although the apparatus of Fig. 2B is arranged specifically for use at only one location, namely, at station No. 1, it will be readily apparent that similar arrangements may be provided at each other location for which nine controls or indications suifice, and at each such location one or ,more of the wires 23 to 25 will be connected to wire 56 or 51 instead of to wire 58 or 59, the

connections at each such location being arranged 22 to the connections for the counting relays at that station.

The initiation .of indication vcodesby the apparatus of Fig.2B is governed by .a group. of three relays, comprising a change relay ICH, a storing relay ICS, and a station sequence relay SS, as will now be described.

It has already been explained that an indication code is initiated by picking up relay ICS to connect wire H to wire 15, and that relaylCS may bepicked up by manual. control by trans-. mitting a control code to station No. 1. An indication code is also initiatedautomatically, in response to a change in position of any ofthe indicating relays which control the character of steps seven to fifteen of the code. In the .specific arrangement shown, a relay R1 controls the character of the seventh element, the eighth and tenth elements are controlled in accordance with the positions of contacts at of switch indication relays NWP and RWP, and the signal relays LHR and RHR similarly control the ninth and eleventh elements. The track relay TR for the detector track section including switch [W controls the character of the twelfth element by the operation of a storing relay TS.

Relay ICH, as shown, is normally held energized over a stick circuit extending from terminal B at contact b of relay RHR over contacts I) of the indicating relays mentioned, and the front contact a and winding of relay ICE to terminal C. Relay ICE is released in response to a change in position of any of these relays to extend the connection from terminal B over its back contact a and front contact a. of a relay SS through the lower winding of relay ICS to terminal C. Relay SS is a slow pick-up relay normally energized over wire I! and consequently is released when the line is in use and becomes reenergized following the release of relay Ll at the end of a code. Relay ICS therefore picks up in response to the closing of contact a of relay SS, after the line has been free for a time suflicient to enable relay SS to pick up, and the closing of front contact b of relay ICS connects terminal B at wire l! to wire l5 to pick up relay ST. In Fig. 2A, wire 28 is connected directly to terminal B, so that relay M picks up atonce to initiate the code. When relay LB picks up in response to the first code impulse, a circuit is closed from terminal B at front contact of relay LB over back contact a of relay CR to wire I 0 and thence over contact c of relay ICS through relay lCH to terminal C, whereby relay ICE is picked up to reestablish its stick circuit. Relay ICS is held energized until the final step of the indication code is transmitted, over a stick circuit including its contact a and wire 20, extending to terminal B at back contact a of relay l6, and thus maintains the coding unit in condition to initiate an indication code repeatedly, if necessary, until such code is transmitted in its entirety.

Relay CR disconnects terminal B from wire In on the eighth step, consequently'a change in the position of any of the indicating relays occurring after relay CR picks up is effective to release relay ICH to effect the transmission of a second code.

An indication code follows each control code received by the station, even though the control code causes no change in the position of any of the indicating relays, for the reason that during each control .code received, the delivery wire 9 is connected to terminalB as already explained, and as 'will be clear from Fig. 2B, relay ICS is thereby energized over its upper winding to establish the stick circuit including its lower w'inding. At the end of a control code, wire 9 remains connected to terminal B until after relay it releases to reestablish the connection to terminal B at wire 22, consequently relay ICS remains picked up.

Relay TS provides means for insuring the transmission of an indication of the occupancy of the track section controlling relay TR, even though the section is vacated before the indication is transmitted. Relay TS picks up in response to the release of relay TR and if relay TR then picks up again, relay TS is held energized over a stick circuit including back contact b of relay ICH until relay ICS picks up, and then over front contact 11 of relay ICH, releasing after the transmission of the corresponding track occupied code, provided relay TR is then energized. When relay ITS releases, its contact b operates to release relay ICI-I to effect the transmission of a track clear code.

In installations having a large number of stations and controlling heavy trafiic it may happen that the number of changes occurring is sufiicient to keep the apparatus in continuous operation for considerable periods of time, resulting in undue delay in the delivery of codes from inferior stations if the stations are given access to the line in a given order of code superiority as described.

Relay SS provides means for preventing undue delay under this condition. Assuming for example, that several stations initiate codes at the same time, it will be evident that the codes will be' transmitted in a fixed order, each relay CS which picks up at the beginning of the series of codes being released at the end of its code, until all are released. When wire I! becomes energized at the end of each code, a relay ST will be picked up to initiate the next code before relay SS has had time to close its contact a. Consequently no additional relays CS can be picked up. In other words, each station unit is allowed to transmit only one code if some other station has a code stored for transmission, for the reason that its relay CS cannot be picked up in response to a change in station conditions unless the line has been free for an interval somewhat longer than the normal interval between successive codes.

Referring now to Fig. 2C, this view together with Fig. 2A shows the apparatus required at a field location at which the number of controlled devices exceeds the capacity of a single ofiice panel, as for example, would be the case in the control of a remotely controlled interlocking as indicated by the track plan in Fig. 11 of my prior patent. In Fig. 20 as shown, it is assumed that the location includes four groups of devices each similar to that of Fig. 2B, comprising stations Nos. to 8, inclusive, of which only station No. 5 is shown.

The code combination required for each of the diiferent stations may be readily ascertained from the connections of the starting button contacts as shown in Fig. 1B. In view of the description of that view and of Fig. 23 already given, it will be readily apparent that the apparatus of Fig. 2C

is connected to respond to the code calls set up by the operation of buttons 5P to 8P, in which step three is long and step four short. These code calls differ one from another only in respect to steps five and six, and the two relays P5 and P6 provide circuits for the selection of four relays 58 to 83 similar to the correspondingly 24 numbered selector relays 05S to 08$ of Fig. 13.

With the apparatus of Fig. 20 in the receiving condition it is clear that any one of the four codes to which it is adapted to respond will suffice for the operation of the maintainers call signal MC, accordingly this feature is arranged as in Fig. 2B.

The circuits for operating the stick polar relays such as relay SWS differ from those of Fig. 2B in that they are selected over contacts of the associated delivery relay 5D, and they are con sequently similar to those for the those for the indication relays K of Fig. 13, already described.

The step-by-step operation of the apparatus of Figs. 2A and 20 in response to a control code transmitted to station No. 5, for example, will now be described.

Assuming the system to be in its normal at rest condition, the operation of the oflice starting button 5PB picks up relays P2, P4, and P5 of Fig. 1B, energizing relay ST of Fig. 1A to pick up relay 05S, thereby connecting terminal B to wire 28 to pick up relay M of the office coding unit to initiate the code, which difiers from the one already described in detail, by having a short fourth step. It is to be understood that the coding unit for stations 5 to 8 is the only one responsive to codes having a long third step and a short fourth step and consequently the only one at which relay 5 picks up. Relay E, Fig. 2A picks up in response to the short first step and prepares a circuit closed when relay Ll releases on the long fourth step, over wire 65, to pick up relay P5, Fig. 2C. Relay Ll reverses relay KS], and the closing of front contact b of relay P5 connects wire 25 to wire 59 extending to terminal C at the reverse contact I) of relay KSI so that relay 6 of the station coding unit picks up in unison with the oflice relay 6, which is energized over a similar circuit. In a similar manner, relay P6 of Fig. 2C is picked up on the sixth step to prepare a circuit for relay 1. At the office and at the location of stations Nos. 5 to 8, relay 1 picks up on step seven, and then on step eight, relays 8 and CR pick up, and at the field location terminal B is connected to wires 2! and 9 to pick up relays 5S and 5D, in turn, and to operate relay MCR in accordance with the character of step 1. The closing of contact a of relay 5D completes a circuit from terminal B through the lower winding of relay 50s to terminal C, so that relay 50S picks up. The closing of contacts b, c, and e of relay 5D connects relays 5WS, ELI-IS, and BRHS to the wires 48, 49, and 5! leading to the coding unit to prepare circuits for operating these relays in accordance with the character of steps eight, nine, and eleven, respectively, as already described. When the sixteenth step is reached, the apparatus restores to normal in the usual manner, but relay 5CH remains picked up over a stick circuit extending from terminal B at back contact of relay 5S over its own front contact a and lower winding to terminal C.

If button 8PB had been operated in place of button 5PB, for example, steps five and six of the code would have been short steps and relays P5 and P6 would have remained released, resulting in the operation of a selector relay 8S and the corresponding delivery relay 8D, not shown, to deliver the code to station No. 8. If, however, due to a fault, relay P5 or P6 at the station fails to pick up on the corresponding long steps of a code for station No. 5, relay 88 is not operated for the reason that in that case the station counting relay 6 or I will not be operated.

The transmission of indication codes by the apparatus of Fig. 2C is effected by the provision of a pair of relays such as the relays 501-1 and 5CS for each group of devices, together with a single relay SS, which relays function like the corresponding relays of Fig. 2B.

In Fig. 20 each relay CS is provided with additional contacts for operating the station pilot relays P over circuits similar to those controlled by the starting buttons PB in Fig. 1B, in other Words, they function as described in connection with relay OICS of Fig. 3, except that the check circuit including wire 28 is omitted. It follows that if relay 508 is picked up, the release of relay L! at the end. of the control code described'completes a circuit from terminal 13 at wire I! over contacts d and e of relay ECS, wires l5and it through relays P5 and P6 to terminal C so that relays P5 and P6 ick up, extending the connection of terminal B over their contacts to wire I to pick up the station starting relay ST, which in turn picks up relays 5S and M to initiate an indication code in which steps one, five, and six are long and steps two and four are short, to select the ofiice panel for station No. 5, and in which steps seven to fifteen are controlled by a group of indicating relays selected by relay 55. It will be clear that in Fig. 2C, the connections from wire H to wires and It are so arranged that if the relays 50S to 80S are all energized at the same time, the corresponding codes will be. transmitted one at a time in order without interference.

Relay SS in Fig. controls the connection to terminal C for the upper winding of each of the relaysE-CS to 8G8, and functions as described in connection with Fig, 23, so that codes for indicating changes occurring after the relays CS have been picked up will be stored. by the relays CH and the corresponding relays CS cannot be reenergized until each of the relays CH energized" at the beginning of the series has transmitted its code.

In the event the office and one or more stations initiate codes at the same time, the transmission of the second impulse by the ofilce transmitter to make the first step short will open the stick circuit for each field station relay M, if closed, and will also pick up relay E at each field location, and at each location such as that of Fig. 20 at which one or more relays P'have been picked up, these relays will be released due to the reversal of the polarity of the current supplied to their stick circuits as already explained in connection with the similar relays of Fig. 13. Consequently only the oflice transmitter remains in operation and the apparatus at each station is in proper condition to respond to a control code containing the corresponding station code call. In Fig. 2C, the release of the P relays prepares a circuit for a selecting relay 88 similar to relay 58 shown, but this relay will not be operatedunlessthe corresponding code call is received so as to enable the counting relays to respond to the first eight impulses of the code.

In view of the similarity of Fig. 20 to 13, it will be readily apparent that additional relays P controlled over one or more of the steps two to seven of the code may be provided to expand the capacity to eight, sixteen, thirty-two, or sixtyfour stations, at the same field location, and that any of the code calls not used at a given location may be used at other locations.

Although I have herein shown and described only one form of remote control apparatus em- 26. bodying my invention and several modifications thereof, itis, understood that various changes and modifications may be made therein within the scope of th appended claims without departing from the spirit and scope of my invention.

Having thus described my invention, what I claim is:

1. A code receiver responsive to codes of impulses arranged to form code elements of two possible characters, comprising a chain of counting'relays including one for each impulse of a code, circuitsfor energizing said' counting relays one at a time in order as the corresponding impulses of a code are received, a pilot relay, a circuit for said pilot relay including a front contact of a particular. counting relay and a contact closed only when the corresponding element has a particular character, means rendering the continued operation of said chain of counting relays dependentupon the position of said pilot relay comprising a contact of said pilot relay and a contact positioned in-accordance with the character of the code element by which said pilot relay and said particular counting relay are controlled in series in the circuit for the next succeeding countingrelay of the chain, two selector relays, and an energizing circuit for each selector relay controlled by the last counting relay in the chain, the circuit for one selector relay including a front contact, and that for the other including a back contact of said pilot relay.

2. A code receiver responsive to codes of impulses arranged to form code-elements of two possible characters, comprising a chain of counting relays including one for each impulse of a code, circuits for energizing said counting relays one at a time in order as the corresponding impulses of a code are received, a group of pilot relays including one for each of a plurality of selecting elements in a code, a circuit for each pilot relay includinga front contact of'the associated counting relay and a contact closed only when the corresponding element has a particular one of said two possible characters, means rendering the operation of said chain of count.-

ing relays dependent upon'the positions of said pilot relays comprising a contact of each pilot relay and a contact positioned in accordance with the character of the code element by which such,

pilot relay and the associatedcounting relay are controlled in series in the circuit for the next succeeding counting relay of the chain, a plurality of selector relays, and an energizing circuit for each selector relay controlled by a counting relay the operation of which is dependent upon the positions .of all said pilot relays, each selector relay circuit including in series front or backcontacts of all saidpilot relays.

'3. A code receiver of the counting relay type,

comprising a chain of counting relays interconnected so they may -be successively energized in response to the elements of an impulse code as received, a series of pilot relays for registering the characters of certain elements of the code,

i a pick-up circuit for each pilot relay including a front contact of the counting relay for the corresponding code element and a contact which is closed only if such element is of a particular character, two sets of contacts for controlling the circuit of the counting relay for the next succeeding element, one set including a front contact of said pilot relay and a contact closed only if the corresponding element is of said particular character, the other including a back contact of said pilot relay and a contact'closed only if the corresponding element is of a difi'erent character,

and a stick circuit for each pilot relay, for holding each energized pilot relay picked up until the end of the code.

4. In a remote control system, a two position line relay, means for operating said relay alternately to said two positions for selected time intervals, two register relays of the stick polar type, two timing devices controlled by the line relay, circuits controlled by one timing device for operating one register relay to normal when the line relay is operated to a first position and to reverse if the line relay remains in its first position for a predetermined time interval, said one register relay being held deenergizedin its last operated position when the line relay is in its second position, circuits controlled by the other timing device for operating the other register relay to normal when the line relay is operated to its second position and to reverse if the line relay remains in its second position for a predetermined tim interval, said other register relay being held deenergized in its last operated position when the line relay is in its first position, and two sets of control circuits one including a normal or reverse contact of said one register relay and a contact of the line relay closed in its second position, the other including a normal or reverse contact of the other register relay and a contact of the line relay closed in its first position.

5. In a code receiver responsive to codes of time spaced impulses, a two position line relay operable to opposite positions in response to the successive impulses of the code, a register relay for each position of said line relay, timing means for each register relay controlled by the line relay for operating such register relay to a normal or reverse position in accordance with the length of time the line relay remains in the corresponding position, means for maintaining each register relay in its last operated position while the other register relay is subject to operation by its timing means, and a series of control circuits adapted to be closed one at a time in order as the successive impulses of the code are received, each including a contact closed in response to the corresponding operation of the line relay and a normal or reverse contact of that register relay the position of which indicates the time interval fol- IOlINiHg the next preceding operation of the line re ay.

6. In a remote control system, a two position line relay operable to opposite positions in response to the successive impulses of a multiple element code, a register relay for each position of said line relay, means effective following each operation of the line relay for operating the corresponding register relay to a normal or reverse position in accordance with the character of the code element being received and for maintaining such register relay in its last operated position while the next succeeding element is being received, a chain of counting relays including one for each element of the code, and circuits for energizing said counting relays one at a time in order in response to successive operations of the line relay, the circuits for certain of said counting relays being adjustably connected over normal or reverse contacts of said register relays as required to render the counting relays selectively responsive to a distinctive combination of code elements.

7. In a remote control system, a two position line relay operable to opposite positions in response to the successive impulses of a multiple element code, a register relay for each position of said line relay, means effective following each operation of the line relay for operating the corresponding register relay to a normal or reverse position in accordance with the character of the code element being received and for maintaining such register relay in its last operated position While the next succeeding element is being received, a group of pilot relays including one for each of a group of selecting elements in each code, means for energizing each pilot relay when the corresponding element is received only if such element is of a particular character, a chain of counting relays including one for each element of the code, and circuits for energizing said counting relays one at a time in order in response to successive operations of the line relay, the circuit for each counting relay for an element following one of said selecting elements including corresponding contacts of the pilot relay for such element and of the register relay by which the character of such element is registered thereby rendering the counting relays selectively responsive to a combination of code elements which corresponds to the positions assumed by said pilot relays.

8. In a remote control system, a two position line relay operable to opposite positions in response to the successive impulses of a multiple element code, a register relay of the stick polar type for each position of said line relay, a chain of counting relays including one for each element of the code, circuits for energizing said counting relays one at a time in order and for energizing said register relays alternately in series therewith in response to successive operations of said line relay, the circuit for each counting relay except the first including a front contact of the next preceding relay of the chain bridged by its own front contact, means for reversing the connections of each register relay when energized without releasing the counting relay in its circuit provided the code element being received is of a particular character, and a plurality of control circuits each including a contact of said line relay, a front contact of a counting relay which is energized during the time such line relay contact is closed, each control circuit also including a normal or a reverse contact of the register relay associated with the next preceding counting relay.

9. In a remote control system, a two position line relay operable to opposite positions in response to the successive impulses of a multiple element code, a register relay of the stick polar type for each position of said line relay, a chain of counting relays including one for each element of the code, circuits for energizing said counting relays one at a time in order and for energizing said register relays alternately in series therewith in response to successive operations of said line relay, the circuit for each counting relay except the first including a front contact of the next preceding relay of the chain bridged by its own front contact, the circuits for certain of said counting relays each including a normal or reverse contact of that register relay which is in series with the next preceding counting relay of the chain, and means for reversing the connections of each register relay when energized without releasing the counting relay in its circuit provided the code element being received is of a particular character.

10, In a remote control system, a two position.

line relay, means for operating said relayalternately to said two positions for selected time intervals, two timing devices, one for each position of the line relay, two register relays of the stick polar type, one for each timing device, means controlled by each timing device for energizing its register relay in the normal direction when the line relay is operated to the corresponding position and for reversing said relay when the line relay remains in such position for a predetermined time interval, each register relay being held deenergized in its last operated position when the line relay is in the position for energizing-the other register relay, a chain of counting relays, circuits for energizing said counting relays successively, so arranged that alternate counting relays are energized in series with one register relay and the remaining counting relays are energized in series with the other register relay, a series of indication relays of the stick polar type including one for each counting relay, and a circuit for energizing each indication relay including a front contact of the corresponding counting relay and a normal or reverse contact of that register relay which is energized in series with the next preecding counting relay.

11. In a code receiver responsive to codes of time spaced impulses, a two position line relay operable to opposite positions in response to successive impulses of a code, a polar relay having normal and reverse contacts adapted to be held in their last operated positions when the relay is deenergized, a circuit for operating said polar relay to close its normal contact closed when the line relay is operated to one position, timing means efiective to reverse said olar relay if the line relay then remains in said one position fora predetermined time interval, a control relay, and an energizing circuit for said control relay closed when the line relay is operated to a position to deenergize said polar relay including that normal or reverse contact which is closed in the last operated position of said polar relay.

l2. Coding apparatus responsive to codes of time spaced impulses comprising a, two position line relay operable to opposite positions in response to successive code impulses, two register relays arranged to be energized alternately as the line relay is operated to its opposite positions, circuits for operating each register relay to a normal position closed when the line relay is operated to a position to energize such relay, timing means effective to reverse the operated register relay if the line relay remains in such position for apredetermined time interval, a storage relay controlled by each register relay, mean for retaining each register relay in its last. operated position as long as the line relay is ina position to energize the other register relay, and circuits including contacts of each register relay for operating the associated storage relay to a position in agreement therewith, closed by the line relay when operated to a position to energize the other register relay.

13. Coding apparatus responsive to codes of time spaced impulses comprising a two position line relay operable to opposite positions in response to successive code impulses, two register relays arranged to be controlled alternately as the line relay is operated to its opposite positions, circuits for operating each register relay to a normal position closed when the line relay is operated to a position to control such relay, timing means effective to reverse the operated register relay if the line relay remains in such position for a predetermined time interval, a chain of counting relayscircuits for energizing said relays one at a time in order in response to successive operations of said line relay, and means for preventing the full response of said chainof relays unless the timing of certain of the impulses is in accordance with a particular code pattern, comprising a normal'or reverse contact of the register relay operated when the line relay is in a given position, in the circuit for that counting relay which is energized in response to the next succeeding operation of the line relay.

14. Coding apparatus responsive to codes of time spaced impulses comprising a two position line relay operable to opposite positions in response to successive code impulses, two register relays arranged to be controlled alternately as the line relay is operated to its opposite positions, circuits for operating each register relay to a normal position closed when the line relay is operated to a position to control such relay, timing means efiective to reverse the operated registed relay if the line relay remains in such position for a predetermined time interval, a group of pilot relays operable in different combinations in accordance with the timing of certain impulses in the code, a chain of counting relays, circuits for energizing said relays one at a time in order in response to successive operations of said line relay, and means for preventing the full response of said chain of relays unless the pilot relays are positioned in accordance with the code pattern of said certain impulses, comprising corresponding contacts of the register relay and of the pilot relay, the operation of which follows the same impulse of the code, in the circuit for that counting relay which is energized in response to the next succeeding operation of the line relay.

15. Coding apparatus responsive to codes of time spaced impulses comprising a two position line relay operable to opposite positions in response to successive code impulses, a register relay of the stick polar type, a pilot relay of the neutral type having pick-up and stick circuits, a circuit for operating the register relay to normal closed when the line relay is operated to one position, timing means set into operation when the line relay is operated to said one position in response to a particular impulse of a code and effective if it remains in that position for a predetermined time interval to pick up said pilot relay and to reversesaid register relay, and a check circuit having two branches closed alternatively to render the coding apparatus responsive to the next operation of said line relay to its other position, one branch including a normal contact of the register relay and a back contact of the pilot relay, the other includinga reverse contact of the register relay and a front contact of the pilot relay.

16. In a remote control system, a code receiver responsive to a series of code elements of selected character, a chain of neutral counting relays, one for each element of the series, two register relays of the stick polar type, circuits for energizing said register relays alternatively and for effecting the successive energization of said counting relays selectively in response to a series of code elements arranged in a particular code pattern comprising circuits for energizing certain alternate counting relays of the chain in response to the corresponding code elements of the series and for energizing one register relay in its normal or reverse direction in accordance with the character of each such element, in series with the ener- 

